On Wed, Mar 07, 2012 at 07:00:14AM +1300, Michael Kerrisk (man-pages) wrote: > Hi Cyrill, > > Just a couple of comments for the moment. > > On Thu, Mar 1, 2012 at 1:23 AM, Cyrill Gorcunov <gorcunov@xxxxxxxxxx> wrote: > > Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > > CC: Tejun Heo <tj@xxxxxxxxxx> > > CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > > --- > > man2/prctl.2 | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 files changed, 104 insertions(+), 0 deletions(-) > > > > diff --git a/man2/prctl.2 b/man2/prctl.2 > > index effad2a..4d6244f 100644 > > --- a/man2/prctl.2 > > +++ b/man2/prctl.2 > > @@ -378,6 +378,110 @@ Return the current per-process machine check kill policy. > > All unused > > .BR prctl () > > arguments must be zero. > > +.TP > > +.BR PR_SET_MM " (since Linux 3.3)" > > +Allows a user to modify certain kernel memory map descriptor fields > > +of the calling process. > > +Usually these fields are set by the kernel and dynamic loader (see > > +.BR ld.so (8) > > +for more information) and a regular application should not use this feature. > > +Still there are cases such as self-modifying programs, where a program might > > +find it useful to change its own memory map. > > By the way, do you have a *simple* program that demonstrates some > usage of R_SET_MM? Hi Michael, well, at moment we've only crtools itself which uses this facility, so if we need complete standalone example I need to think about it. > > > +The kernel must be built with > > +.BR CONFIG_CHECKPOINT_RESTORE > > +option turned on, otherwise this feature will not be accessible > > +from a user space level. > > +The calling process must have > > +.BR CAP_SYS_ADMIN > > +(see > > +.BR capabilities (7) > > +for details) capability granted. > > As we discussed earlier (offlist), there are probably better choices > than the hugely overloaded CAP_SYS_ADMIN (see > http://man7.org/linux/man-pages/man7/capabilities.7.html). And if the > capability governing PR_SET_MM is to change, then it would be good to > do so before 3.3 is released. What are the plans on this point? > Yeah, I thought about changing it to CAP_SYS_RESOURCE here. And I'll post a patch. The problem at moment that there another two snippets needed for prctl -- ability to set new /proc/pid/exe symlink and to obtaine clear-tid-address. So there is a discussion now about symlink change. Once we finish with it -- i'll post update for capability. If you prefer to have it done earlier -- no problem, I'll cook a patch today instead on top of everything we've already merged into linux-next. What would you prefer? Cyrill -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
